Textured polyethylene terephthalate yarns

ABSTRACT

Textile articles comprise continuous filament yarns (or staple fibers obtained therefrom) of polyethylene terephthalate or another thermoplastic material, in which the individual filaments are of alternately decreasing and increasing thickness, the thinnest zones having the highest crystallinity index and molecular orientation and vice versa, but all the zones having a certain index of crystallinity, each filament having a non-spiral three dimensional crimp and a high apparent volume. The yarns are made by partially stretching the initial yarn in a crack or figure promoting agent, and relaxing the stretched yarn in two or more stages, in at least the last of which it is heated, preferably with a high temperature-time gradient.

United States Patent Michel [4 1 Aug. 1, 1972 [54] TEXTURED POLYETHYLENEPrimary Examiner-Robert F. Burnett TEREPHTHALATE YARNS AssistantExaminer-Raymond O. Linker, Jr.

Arr -C h ,D b h [72] Inventor: Buzano Michel, Villeurbanne omey us manat y&cus man Rhone, France 57 ABSTRACT Assignee: SodeteRhodiacetarparisv France Textile articles comprise continuous filamentyarns [22] Filed: Sept. 23, 1970 (or staple fibers obtained therefrom)of polyethylene terephthalate or another thermoplastic material, in [2Apri 3 which the individual filaments are of alternately Related US.Application Data decreasing and increasing thickness, the thinnest zoneshaving the highest crystallinity index and molecular orientation andvice versa,'but all the zones [62] Division of Ser. No. 799,794, Feb.17, 1969.

havmg a certain index of crystalllnity, each filament 52 us. (:1..57/140J,16l/173, 161/179 having a "On-Spiral three dimensional Crimpand a 51 Int. Cl. ..D02g 3/00 high apparent The Yams are made byPartially [58] Field of Search 161/173 57/140 R 140 S stretching theinitial yarn in a crack or figure promoting agent, and relaxing thestretched yarn in two or morestages, in at least the last of which it isheated, [56] References Cited preferably with a high temperature-timegradient.

UNITED STATES PATENTS I 2 Claims, 4 Drawing Figures 3,l85,613 5/1965.Adams ..l6l/174 PATENTEDMIB 1 I972 FIG-3;

TEXTURED POLYETHYLENE TEREPHTHALATE YARNS CROSS REFERENCE TO RELATEDAPPLICATIONS This is a division of copending US. Pat. application Ser.No. 799,794 filed Feb. 17, 1969.

This invention relates to a new textile article comprising texturedyarns of high apparent volume having a three-dimensional non-spiralcrimp, and to a process and a device for the manufacture of such yarns.

A large variety of so-called textured yarns already exists, and thesecan be schematically-classified into spirally crimped yarns andnon-spirally crimped yarns. The former are obtained by twisting, settingand untwisting, generally by means of a continuous false twist process.These yarns are noteworthy for a high elasticity which must for certainapplications be reduced by means of a supplementary setting treatment.

The non-spirally crimped yarns have crimps of various configurations andare generally much less elastic, which is usually not undesirable. Theyare obtained by various processes, using mechanical, pneumatic ormechanical-pneumatic devices. These processes suffer from thedisadvantage of a relatively limited production speed as a result of thefact that moving elements are used.

Chemical processes have also been used to texture yarns. In fact itappears logical a priori to hope to obtain reproducible results moreeasily by chemical means.

However this method of texturizing has hitherto remained littledeveloped because the processes which have been discovered have notgiven industrial results comparable to those obtained by mechanicalmeans such as for example by false twist.

It was observed a long time ago that polyamide yarns can be cold-drawnmore easily when moistened with water or with a hydroxylated non-solventsuch as a lower aliphatic alcohol, a glycol or a hydroxyester.

It has been proposed to manufacture a crimped yarn by moistening anunstretched or partially stretched polyamide yarn with water, colddrawing, drying it in the untensioned state, and subjecting it to a heattreatment before or after the cold drawing but before the untensioneddrying.

It was later shown that stretching synthetic yarns in such baths causesthe formation of cracks or surface fissures. Starting from thisobservation, a process for the manufacture of slub yarns has beenproposed in which the yarns are tensioned while in contact with a crackpromoting agent, stretched to at least 1.01 times, and in general toapproximately 2.5 times, their initial length, withdrawn from theinfluence of the crack promoting agent, and stretched to produce a slubyarn having an oriented structure.

It has also been proposed to manufacture textured yarns from a yarnwhose structure has been rendered asymmetric during spinning by theaction of a cooling agent, by tensioning it while it is in contact witha bath containing a crack promoting agent, moistening it with a liquidmedium which is free from crack promoting agents, and stretching it inthe moistened state. Yarns of a cracked structure have also beenmanufactured by maturing in a bath containing a crack promoting agentwith gentle stretching and then withdrawing the yarns from the bath andstretching them strongly. However, apart from the fact that this processdoes not produce textured yarns but yarns having a ribbed surface, itrequires several days to carry out.

All these methods either produce a product such as a slub yarn whichcannot pretend to replace a textured yarn, or provide a textured yarnbut use, at some stage another conventional process for obtaining atextured yarn such as asymmetric cooling of the yarn during spinning,which is an operation which is delicate to carry out.

In one aspect the present invention consists in a new textile articlewhich comprises continuous multifilament yarns, or staple fibersobtained from such yarns, of a synthetic thermoplastic material in whicheach filament comprises alternating zones in which its diameterincreases and decreases progressively between at least two diflerentmean values, in which the zones of the lowest diameter correspond to thezones having the highest crystallinity index and a higher molecularorientation, each filament having a non-spiral threedimensional crimpand a high apparent volume, all the zones in each filament having apositive degree of crystallinity.

While these textile articles can be made of any synthetic thermoplasticmaterial, they are preferably made of a polyester, e. g. polyethyleneterephthalate.

In the case of polyethylene terephthalate the crystallinity index of thethin zones is preferably between 15 and percent, advantageously between20 and 40 percent, and the crystallinity index of the thick zones ispreferably less than 25 percent and advantageously between 5 and 25percent. The molecular orientation of the thin parts is greater thanthat of the thick parts, the angle of orientation t of these thin partsbeing advantageously less than 45. Further, the diameter of the thickzones is at least 1.01 times, and advantageously 1.05 to 1.20 times,that of the thin zones.

The overall crystallinity index value is determined by the method ofW.0. Statton [Journal of Applied Polymer Science, Vol. 7, pages803-815-(1963)], and the values for the angle of orientation by the method ofW.A. Sisson [Journal of Textile Research, vol. 7, Page 425-(1937)]. Thevalues of the crystallinity indices and of the orientation angles forthe various zones are determined taking into account the crystallinityindices and overall orientation of the yarn, the proportions by volumeof the various zones, the appearance of the X- ray crystallograms,comparisons of fluorescence after dyeing various zones of one and thesame yarn or of several yarns, and the morphology of these zones.

Like the synthetic textured yarns, especially those based on apolyester, obtained by stretching in contact with a crack promotingagent and heat treatment in the relaxed state in a single stage, theyarns of the invention show an improved swelling, a dyeing affinitywhich makes it possible to dye them without carriers, and a relativelylow shrinkage in boiling water, combined with good mechanicalproperties, especially tensile strength, and good dimensional stability,which is retained even under the influence of mechanical and/ or thermalfactors. This amounts to saying that the textured yarns of the inventionhave properties which in the past have been difficult to obtainsimultaneously,

such as good dimensional stability, sufficient breaking load, and greatflexibility.

The invention consists also in a process for the texturizing of acontinuous multifilament yarn of a synthetic thermoplastic material,especially of a polyester, by partial stretching of such a yarn incontact with a crack promoting agent followed by heat treatment in therelaxed state, in which the stretched yarn in contact with a crackpromoting agent is relaxed in at least two stages, at least the last,and preferably each, of which is accompanied by a heat treatment. Thelast heat treatment is advantageously carried out with heat shock, i.e.is a heat treatment carried out with a sharp temperature gradient.

The crack promoting agent used can be of any known type such as analcohol, a glycol, dimethylformamide, kerosene, perchlorethylene, apolyoxyethylenic liquid of the Carbowax type, pyridine, etc. Suchcompounds are frequently described in the literature. Preferably,relatively cheap agents such as the lower alcohols are employed.

The multiple relaxation can take place continuously or as two or moreseparate operations. In one practical application of the invention, theyarn is in a continuous way stretched in contact with a crack promotingagent, and subjected to two successive heat treatments in an at leastpartially relaxed state, the second being effected with heat shock;preferably also this second treatment is carried out on an article, e.g.a woven or knitted article, while it is completely relaxed and free fromtension. This second treatment can be accom panied by a dyeing treatmentand can be followed by a third heat treatment in which the yarn or otherarticle is dried under tension. In the case of a woven fabric, this lasttreatment can be effected on a center frame and does not change theproperties of the yarn which has been stabilized by the earlieroperations, in particular the heat shock of the second treatment.

The invention also comprises a device for carrying out the aboveprocess, which comprises means for feeding the yarn, means forstretching it in a containing a crack promoting agent bath, means forrelaxing it, optionally combined with heating means, and wind-up means.This device can also comprise means for carrying out treatments whichare additional to, but are carried out simultaneously with, that of theinvention, such as for example devices for dyeing comprising a porouswall such as described in French Pat. No. 1,502,746 of the ApplicantCompany.

The invention will be more particularly described by reference to theaccompanying Drawing, in which:

FIG. 1 is a schematic view of the device used,

FIG. 2 is a schematic view of a device, in which the yarn issimultaneously dyed on a porous wall,

FIG. 3 is a schematic representation of a filament or yarn preparedaccording to the present process but without heat shock,

FIG. 4 is a schematic representation of the same filament but treatedwith heat shock.

Referring now to FIG. 1, a bobbin 2 mounted on a creel 1 delivers asynthetic unstretched yarn 3 which is drawn off by the feed rollers 4and 5 after passing through a wire thread guide 6. g

The yarn 3 is brought into contact with a crackpromoting agent in a vat7 and is stretched between the system of feed rollers 4 and 5 and afirst set of stretching rollers 8 and 9, and is then relaxed betweenthis set of rollers and a set of relaxing rollers 10 and l 1 whilepassing over a heating plate 12. The yarn thereafter passes into aheating box 13 where it undergoes a second heat treatment in thecompletely relaxed state, being then forwarded by relaxing rollers I 14and 15 running at a lower peripheral speed than the rollers 10 an 11.The yarn is thereafter wound up on a spindle 16 by means of atraveller-ring system.

In a variant process, the heating box 13 is omitted and the yarnundergoes its second heat treatment in the relaxed state either during adyeing treatment or during some other finishing operation. This secondheat treatment can be carried out either on the yarn or on a fabricproduced from the yam.

In another variant process, a dyeing device such as that described inFrench Pat. No. 1,502,746 is introduced between the heating plate 12 andthe set of rollers 10 and 11; this device is illustrated in FIG. 2, andcomprises a porous partition 20 having a smooth essentially planesurface through which the treatment liquid passes, positionedtransversely in a tube 21 very close to its end. The yarn 3passesvertically at high speed in front of the operating surface of the porouspartition, between it and a cover 22. The travel of the yarn near theporous partition is controlled by two guide elements 23 and 24. Theporous wall is fed with liquid via a pipeline 25.

In the illustrative Examples which follow the polyethylene terephthalateused has an intrinsic viscosity in o-chlorophenol of the usual value fortextile yarns, e.g. of the order of 0.65.

EXAMPLES l to 5 Using the device for the first variant described above,a 22 filament yarn of polyethylene terephthalate, of filament denier 7,is stretched by a factor of 3 in an aqueous bath containing 25 percentof ethanol at ambient temperature, and is then relaxed to variousdegrees and at various temperatures of the plate 12. The yarn isthereafter heat treated in the completely relaxed state by immersing itin water at 40 C., progressively raising the temperature of this waterto C., and keeping the yarn at this temperature for 5 minutes. The yarnis thereafter dried without tension while freely exposed to the air andis then heated in an oven for 5 minutes at C.

The degree of relaxation is set by the overfeed of the yarn between theset of rollers 8, 9 and the set of rollers 10, 11.

The results obtained are given in the Table below:

The bulk is as given by the Koningh test.

The crimp effect is determined by measuring a length l of the yarn undera load of 0.05 g/den, and then leaving the yarn for 24 hours under aload of 0.001 g/den and again measuring the length 1 The crimp effect isgiven by the ratio (l -1 X (100).

The shrinkage in boiling water is determined in the following manner: alength L, (measure under a load of 0.05 g/den) of the yarn is dippedinto boiling water for 2 minutes, dried in an oven at 100 C. for 30minutes, and suspended and left at rest for minutes; the load of 0.05g/den is then again applied, and the new length L of the yarn ismeasured, the shrinkage in boiling water being given by the formula:

( A D/(L1) X The residual shrinkage of the yarn in steam at 130 C. ismeasured in the same manner, except that the yarn, in place of beingimmersed in boiling water for 2 minutes, is placed in an autoclave inwhich the temperature rises to 130 C. over 15 minutes, the yarn remainsat 130 C. in the saturated steam for a further 15 minutes.

The creep is given by the permanent deformation assumed by a yarn afterapplying a load of the order of 40 percent of the breaking load.

EXAMPLE 6 A polyethylene terephthalate yarn of the same structure as inExample 1 is stretched by a factor of 3 in an aqueous bath containing 25percent of ethanol at ambient temperature. This yarn is then relaxed by2.9 percent without heat treatment, that is to say without using theheating plate 12.

The yarn is then given a treatment identical with the second heattreatment of Example 1.

The yarn obtained has the following characteristics:

Shrinkage in boiling water 14.7 Shrinkage in steam at 130C. 17.40% CrimpSponge effect in l.0l Bulk in cm lg 1.4 Creep in 0.7

EXAMPLE 7 The purpose of this Example is to demonstrate the advantage ofheat shock during the second heat treatment.

A polyethylene terephthalate yarn of the same structure as before isstretched by a factor of 3.3 in an aqueous bath containing 25 percent ofethanol at ambient temperature. This yarn is subjected to a first heattreatment on the plate 12 at a temperature of 195 C., with a relaxationof 22.5 percent.

The yarn is thereafter developed by means of a second heat treatment insteam in the completely relaxed state, firstly without heat shock, byplacing the yarn above a vessel containing water and raising the waterto the boil, so causing a relatively gradual evolution of steam, andsecondly with heat shock, by suddenly introducing the yarn into thechamber filled with steam at the same temperature as before.

FIGS. 3 and 4 give a schematic representation of a constituent filamentof this yarn after treatment without and with heat shock respectively.

In the first case the filament has a mean diameter of p. and thevariations in diameter are very slight.

in the second case the mean diameter is slightly increased to 21 1., andthe mean diameter of the thick parts is 23;.t.

It is found that the heat shock slightly disorients the thickest zonesof the filament, causing greater shrinkage and slubbing, accompanied bya greater crimp, the yarn which has been treated without heat shock infact having 56 half-waves, and the yarn which has been treated with heatshock having half-waves, both over a length of 10 cm.

The second yarn furthermore has a filament denier of 3.3 as opposed to3.04, and its elongation at break is 93 percent instead of 81 percent.The tenacity of both yarns is about 3.3 g/den., the shrinkage in boilingwater 12 percent, the crimp effect 1.05 percent, the bulk 1.6 em /g andthe creep 1.0 percent.

In both cases the molecular structure is essentially the same; the thinparts have a mean crystallinity of 20 to 25 percent and a good molecularorientation (angle f) 25 to 30). The thick parts are unoriented andtheir crystallinity index is about 10 percent, the mean crystallinityindex of the yarn being about 20 percent.

Yarns according to the invention yield fabrics of pleasant appearanceand handle, and furthermore possess particularly valuable dyeingaffinity, as can be demonstrated in the following manner:

A yarn according to the invention and a standard polyethyleneterephthalate yarn are both dyed with a mixture of dyestuffs consistingof:

0.3 percent by weight of Disperse Orange 11 0.4 percent of DisperseViolet 1 (C.l. 61,100

and

4 percent ofDisperse Blue 9 (C.l. 61,115).

(The names of the dyestuffs are those in the Color Index). Two piecesknitted with a mixture of these two yarns are dyed by immersion in abath which is initially at 40 C., and which is then heated progressivelyat a rate of temperature rise of 1 C. per minute up to 90 C., at whichit remains for 90 minutes.

It is found that the standard yarn has not been dyed, while the yarn ofthe invention has assumed a navy blue shade with good fastness towashing, to perspiration and to light, as shown by the following resultsmeasured according to the measurements of the E.C.E. Code (2nd. edition,1958 and supplements). (This E.C.E. Code is published by The Associationfor the Study and Publication of Methods for the Determination ofFastness Properties, 12 rue dAnjou, Paris 8.)

Fasmess to washing at 60C. Fastness to perspiration Fastness toartificial light The same experiment is repeated, but this time adding 7g/liter of a carrier, namely sodium o-phenylphenate, to the dyeingcomposition. The standard yarn still does not accept the dye, while theyarn according to the invention shows a slightly more intense navy blueshade than in the preceding experiment.

As illustrated by these Examples it is possible, by means of the presentinvention, directly and continuously to obtain, from extrusion spinning,a bulk textured synthetic yarn which is dimensionally stable, easy todye, particularly valuable in knitting and weaving, and able to suit allother textile applications either in the form of a continuous yarn or inthe form of staple fibers.

What is claimed is:

1. Textile articles comprising multi-filament polyethylene terephthalateyarns, in which each filament consists of alternating zones whosediameter progressively increases and decreases respectively between atleast two different mean values, the parts of lowest diameter having thehighest crystallinity index l

2. Textile articles according to claim 1, in the form of continuousmultifilament yarns.